The present invention relates to a photovoltaic generation system capable of obtaining electric power by means of photovoltaic cells arranged on, for example, a roof of a building, and a wiring apparatus and a wiring structure for conducting electric power produced by the generation system into the building such as a house.
A photovoltaic generation system comprises generating sections each including a plurality of photovoltaic modules, which can generate outputs corresponding to a desired power generation, and wiring apparatuses for conducting the outputs of the generating sections to an inverter unit and the like in a building or house. The generating sections include photovoltaic modules, each formed of a plurality of photovoltaic cells connected in series or parallel with one another, or photovoltaic module units, each formed of a plurality of photovoltaic modules combined together. Normally, one photovoltaic module has one terminal box. The terminal box has two output terminals for positive and negative electrodes. Electric power generated by the photovoltaic module is outputted via the terminal box.
In this power generation system, the module units that are arranged side by side are connected in series and/or parallel with one another. Described in Jpn. Pat. Appln. KOKAI Publication No. 7-131045 is a wiring apparatus that can be suitably used to connect a plurality of photovoltaic modules in series with one another. This prior art, as shown in FIG. 24, wiring apparatus comprises a trunk 1, which includes a pair of electric wires 2 and 3, and branch lines 4 connected in series with one of the wires 2 and 3 of the trunk 1. These branch lines 4 are connected at given spaces in the longitudinal direction of the one wire 2. Connecting portions 5 that are connected to the respective output terminals 6 of the module units 7 are provided on the respective distal end portions of the branch lines 4, individually. This prior art wiring apparatus has a two-core, series-connected structure.
Other conventional wiring apparatuses than the prior art example described above comprise electric wires that are connected individually to the respective output terminals of a plurality of photovoltaic modules or the respective positive and negative output terminals of a plurality of photovoltaic module units. These electric wires are led into a building.
According to the above-described structure in which a large number of wiring apparatuses are connected for each output terminal of each photovoltaic module or module unit and are all led into the building, the wire length of each wiring apparatus that extends from each output terminal of each module or module unit to the interior of the building is substantial. Accordingly, the entire photovoltaic generation system requires use of a lot of electric wires. Besides, a lot of wiring apparatuses are needed. In the case of a photovoltaic generation system that uses 120 photovoltaic modules, for example, the photovoltaic module units are 20 in all if each module unit is formed by connecting six photovoltaic modules in series with one another. In this case, therefore, the wiring structure of the prior art example in which all the electric wires connected individually to the photovoltaic module units are led into the building requires use of 40 single-core wiring apparatuses or 20 two-core wiring apparatuses. The use of the two-core, series-connected wiring apparatuses only ensures the formation of photovoltaic module units that each include a plurality of photovoltaic modules connected in series with one another. The two-core wiring apparatuses can not connect photovoltaic modules in parallel.
Thus, fetching outputs conventionally requires use of many wiring apparatuses, so that the installation of the photovoltaic generation system on a roof or the like costs much labor. Accordingly, there is a high possibility of misconnection. Since a large hole for a lot of wiring apparatuses must be bored through a wall of the building, so that sealing the building against rainwater and the like entails labor.
The conventional wiring apparatuses extend long from the respective output terminals of the photovoltaic modules or module units into the building. Therefore, the wiring apparatuses that are connected to the photovoltaic module units and the like are liable to hinder maintenance operation for the modules and other elements. Since the existing wiring apparatuses cannot be made longer, moreover, they cannot cope with extension of the photovoltaic modules.
In the case where a plurality of photovoltaic modules or module units are connected in series with one another, connection is made by using dedicated wiring apparatuses for series connection, such as the one described in the aforesaid publication. In the case where a plurality of photovoltaic modules or module units are connected in parallel with one another, connection is made by using dedicated wiring apparatuses for parallel connection. Thus, the wiring apparatuses used are varied in type, and their productivity is poor. Besides, prearrangement for laying operation, as well as the laying operation itself, is complicated. If the connection of the wiring apparatuses requires change to cope with the extension of the photovoltaic modules or maintenance operation, it cannot be achieved with ease.
In wiring apparatuses represented by the aforesaid two-core wiring apparatuses that comprises a trunk and branch lines, branch junctions of the branch lines are expected to be molded from synthetic resin. Possibly, however, outdoor portions of the wiring apparatuses may be exposed to rainwater, so that the branch junctions require high reliability to resist penetration of water.